Hydrocephalus and Aquaporins: The Role of Aquaporin-1

Abstract

Aquaporins (AQPs) are membrane proteins that facilitate water and small solute movement in tissues. Hydrocephalus is a major central nervous system disorder associated with defective cerebrospinal fluid (CSF) turnover. Aquaporin-1 (AQP1) is a water channel located mainly at the choroid plexus epithelium and plays an active role in CSF production. The aim of this study is to review the pertinent literature concerning the role of aquaporin-1 in the pathophysiology of hydrocephalus. We performed a MEDLINE search using the terms aquaporin AND hydrocephalus. The results of the search were further refined to exclude studies not related to aquaporin-1. Five studies were identified. Three of these studies utilized an animal model, while only two studies referred to a few human cases of hydrocephalus. Most of the studies indicate that there is a down-regulation of AQP1 expression in choroid plexus in models of hydrocephalus. A small series of human choroid plexus tumors showed that AQP1 expression is up-regulated. In cases of human choroid plexus tumors, there are indications that AQP1 may have alternative physiologic roles, but it is not clear whether this is associated with a specific type of hydrocephalus or the genetic burden of the tumor. There has been a paucity of research on the link between aquaporins and hydrocephalus. Most studies have relied on animal models. An adaptive and protective role of AQP1 as a regulator of CSF production is proposed in the pathophysiology of hydrocephalus. Further research is needed to clarify if this association exists in humans.